Foreign Language Syndrome: Neurological and Psychiatric Aspects

Foreign Language Syndrome (FLS) is a rare neuropsychiatric condition characterized by the sudden, involuntary use of a non-native language, with concurrent loss or suppression of the native language. Distinct from Foreign Accent Syndrome (FAS), FLS often arises acutely following anesthesia, brain injury, or psychological stress. Although neuroimaging typically reveals no structural pathology, functional disconnection within bilingual language control systems has been hypothesized. Case reports suggest contributions from both neurological disruptions-such as transient cortical dysfunction-and psychiatric mechanisms, including dissociation and conversion phenomena. This review synthesizes the clinical features, diagnostic strategies, neurocognitive models, and psychiatric interpretations of FLS. It emphasizes the importance of multidisciplinary evaluation and treatment and outlines prognosis patterns. The need for longitudinal follow-up, functional imaging studies, and centralized case databases is highlighted to better understand the pathophysiology and clinical management of this enigmatic syndrome.